There are essentially two ways to protect the bearings against the described phenomenon: either the roller bearing is isolated, or an electrically conductive link is fitted between the inner ring and the outer ring. The first way is adopted, for example, in DE 100 37 423 A1 or DE 41 00 587 C2, and the second is adopted in EP 892 471 B1.
In DE 100 37 423 A1, an isolating ring is provided between the outer ring and the housing, adversely affecting the seating of the bearing ring, and making installation more difficult. The sliding metallic link in EP 892 471 B1 touches the respective other bearing ring only at points, or at best on a line, as a result of which it can transmit only very low current levels, but not current levels of several amperes. Furthermore, the links are susceptible to wear, and are therefore not reliable in the long term. In EP 892 471 B1, in addition to the metallic link, the roller bearing additionally contains a grease, which is made conductive by the addition of electrically conductive solid particles. The fact that the grease is used in addition to the link indicates that neither the link nor the grease on their own would be sufficient to produce a reliable conductive connection.